Key result
The p.Y4864H mutation in RyR1 alters calcium channel function, which is the likely cause of muscle weakness in Central Core Disease, rather than the associated reduction in RyR1 protein amount.
The muscle weakness in CCD patients with the p.Y4864H mutation is likely due to altered calcium channel function rather than a simple reduction in RyR1 protein amount.
BACKGROUND: Central Core Disease (CCD) is a congenital myopathy often resulting from a mutation in RYR1 gene. Mutations in RyR1 can increase or decrease channel activity, or induce a reduction in the amount of protein. The consequences of a single mutation are sometimes multiple and the analysis of the functional effects is complex. OBJECTIVE: The consequences of the p.Y4864H mutation identified in a CCD patient have been studied regarding both RyR1 function and amount. METHODS: The amount of RyR1 in human and mouse muscles was evaluated using qRT-PCR and quantitative Western blot, and calcium release was studied using calcium imaging on primary cultures. The results were compared between human and mouse. RESULTS: The p.Y4864H mutation induced an alteration of calcium release, and in addition was associated to a reduction in the amount of RyR1 in the patient's muscle. This suggests two possible pathophysiological mechanisms: the alteration of calcium release could result from a modification of the channel properties of RyR1 or from a RyR1 reduction. In order to discriminate between the two hypotheses, we used the heterozygous RyR1 knockout (RyR1+/-) mouse model showing a comparable RyR1 protein reduction. No reduction in calcium release was observed in primary muscle culture from these mice, and no muscle weakness was measured. CONCLUSIONS: Because the reduction in the amount of RyR1 protein has no functional consequences in the murine model, the muscle weakness observed in the patient is most likely the result of a modification of the calcium channel function of RyR1 due to the p.Y4864H mutation.
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Cacheux et al. (2015) studied Central Core Disease. p.Y4864H mutation in RyR1 vs. Heterozygous RyR1 knockout (RyR1+/-) mouse model was evaluated on Calcium release and amount of RyR1 protein. The p.Y4864H mutation in RyR1 alters calcium channel function, which is the likely cause of muscle weakness in Central Core Disease, rather than the associated reduction in RyR1 protein amount.
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